scheduler: Replace kInternalAccessibility with kInternalDefault and deprectate...

scheduler: Replace kInternalAccessibility with kInternalDefault and deprectate kInternalAccessibility

Following the guideline https://bit.ly/2vMAsQ4, we determined to use
kInternalDefault as long as the tasks can run in the default way, that
might be throttled or paused. This CL deprecates kInternalAccessibility
whose task runner is a default task runner.

Bug: 836410
Change-Id: Icaa3532e3ef2563b8baa6436566cc5f1ac036b86
Reviewed-on: https://chromium-review.googlesource.com/1032318
Commit-Queue: Hajime Hoshi <hajimehoshi@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#557109}

content/renderer/accessibility/render_accessibility_impl.cc

@@ -334,7 +334,7 @@ void RenderAccessibilityImpl::HandleAXEvent(const blink::WebAXObject& obj,
     // When no accessibility events are in-flight post a task to send
     // the events to the browser. We use PostTask so that we can queue
     // up additional events.
-    render_frame_->GetTaskRunner(blink::TaskType::kInternalAccessibility)
+    render_frame_->GetTaskRunner(blink::TaskType::kInternalDefault)
         ->PostTask(FROM_HERE,
                    base::BindOnce(
                        &RenderAccessibilityImpl::SendPendingAccessibilityEvents,

third_party/blink/public/platform/task_type.h

@@ -11,6 +11,8 @@ namespace blink {
 // This enum is used for a histogram and it should not be re-numbered.
 //
 // For the task type usage guideline, see https://bit.ly/2vMAsQ4
+//
+// When a new task type is created, use kCount value as a new value.
 enum class TaskType : unsigned {
   ///////////////////////////////////////
   // Speced tasks should use one of the following task types
@@ -163,11 +165,6 @@ enum class TaskType : unsigned {
   // Tasks related to animation like blinking caret or CSS animation.
   kInternalAnimation = 34,
 
-  // Tasks related to accessbility. Tasks with this type are mainly posted by:
-  // * //content/renderer/accessibility
-  // * //third_party/blink/renderer/modules/accessibility
-  kInternalAccessibility = 35,
-
   ///////////////////////////////////////
   // The following task types are DEPRECATED! Use kInternal* instead.
   ///////////////////////////////////////

third_party/blink/renderer/modules/accessibility/ax_object_cache_impl.cc

@@ -108,7 +108,7 @@ AXObjectCacheImpl::AXObjectCacheImpl(Document& document)
       modification_count_(0),
       relation_cache_(new AXRelationCache(this)),
       notification_post_timer_(
-          document.GetTaskRunner(TaskType::kInternalAccessibility),
+          document.GetTaskRunner(TaskType::kInternalDefault),
           this,
           &AXObjectCacheImpl::NotificationPostTimerFired),
       accessibility_event_permission_(mojom::PermissionStatus::ASK),

third_party/blink/renderer/platform/scheduler/child/worker_scheduler.cc

@@ -71,7 +71,6 @@ scoped_refptr<base::SingleThreadTaskRunner> WorkerScheduler::GetTaskRunner(
     case TaskType::kInternalUserInteraction:
     case TaskType::kInternalInspector:
     case TaskType::kInternalAnimation:
-    case TaskType::kInternalAccessibility:
       // UnthrottledTaskRunner is generally discouraged in future.
       // TODO(nhiroki): Identify which tasks can be throttled / suspendable and
       // move them into other task runners. See also comments in

third_party/blink/renderer/platform/scheduler/main_thread/frame_scheduler_impl.cc

@@ -286,7 +286,6 @@ scoped_refptr<base::SingleThreadTaskRunner> FrameSchedulerImpl::GetTaskRunner(
     case TaskType::kIdleTask:
     case TaskType::kInternalDefault:
     case TaskType::kMiscPlatformAPI:
-    case TaskType::kInternalAccessibility:
       // TODO(altimin): Move appropriate tasks to throttleable task queue.
       return TaskRunnerImpl::Create(DeferrableTaskQueue(), type);
     // PostedMessage can be used for navigation, so we shouldn't defer it

third_party/blink/renderer/platform/scheduler/main_thread/main_thread_scheduler_impl.cc

@@ -180,8 +180,6 @@ const char* TaskTypeToString(TaskType task_type) {
       return "InternalInspector";
     case TaskType::kInternalAnimation:
       return "InternalAnimation";
-    case TaskType::kInternalAccessibility:
-      return "InternalAccessibility";
     case TaskType::kCount:
       return "Count";
   }